TPS22810: How to use it for inductive loads (12vdc water on/off valve)

Part Number: TPS22810

Where can I find information on how to use this switch for inductive loads? Datasheet has no information whatsoever.

Thanks.

4 Replies

  • Hi Regis,

    The TPS22810 is unable to withstand the negative transients from switching an inductive load (abs min rating is only -0.3V). We do not recommend this device for inductive switching.

    For driving inductive loads, you could take a look at low side drivers, like the ULN2003A.

    Thanks,

    Alek Kaknevicius

  • Hi Regis,

    A bit more information for you:

    At a bare minimum, if you needed to drive an inductive load with a load switch, you would need a diode in parallel with the inductance (flyback diode). However, when the inductive load is switched, the transients will cause current to flow backwards through the body diode of the pass FET of the TPS22810.

    In our high side switches, we characterize the amount of energy the body diode can take due to inductive switching. An example of this is the TPS1H100-Q1 which specs an "inductive load switch-off energy dissipation single pulse" value of 70mJ. We do not do this same characterization on our load switches, so we would not be able to provide an estimate on the capability of our body diodes. To protect the body diode, an external diode would need to be put in parallel, from VOUT to VIN.

    Out of curiosity, what is the application and what kind of a load are you trying to drive? 

    Thanks,

    Alek Kaknevicius

  • In reply to Aleksandras_Kaknevicius:

    Dear Alek,

    Thanks for your prompt reply.

    Based on your feedback, I decided to make a little mod in the design and have a little more control over the water valve guided by the impossibility of switching inductive loads by my chosen switch.

    Price is an issue, so I will still use the TPS22810 for the hi side switch and a TPL7407 for the low side. You asked for the reason I chose the TPS22810, and that is because those 2 12Vdc water valves are external to the apparatus and may get shorted to ground or shorted together during maintenance or whatnot... Having the "live" 12 Vdc directly out can destroy the internal power supply, hence the hi side switch with short circuit and over current protection.

    The added modification is using the TPL7407 so I can have full 12v applied and then reducing (by PWM) the voltage to a "holding" level since the valves get pretty warm with the full voltage.

    This mod creates a new set of details:

    1) Now the back EMF goes to the diode internal to the TPL7407 and when the PWM takes control of the switching, it will cause some noise at the TPS22810 minimized by the output capacitor but still noisy (yeah, I know, nobody likes that...).

    2) by the specs of the TPL7407, it is designed to withstand that back EMF. I will use 3 in parallel to drive each of the 2 valves in opposing PWM phases to minimize noise over the switch output.

    Note: Each valve consumes 0.5 amps when steady on.

    The ground pin of the TPL7407 will have a very small resistor for the reading of the current trough it so the mcu can detect faulty currents and notifies the user of the fact, and before you say that the TPL7407  may goes into a negative analog feedback for the excess voltage on the ground pin, the IR will be less than it's  Vin low spec.

    Thanks.

    Regis.

  • In reply to Regis:

    Hi Regis,

    Thanks for your description! My only concern is your statement here: 

    You asked for the reason I chose the TPS22810, and that is because those 2 12Vdc water valves are external to the apparatus and may get shorted to ground or shorted together during maintenance or whatnot... Having the "live" 12 Vdc directly out can destroy the internal power supply, hence the hi side switch with short circuit and over current protection.

    The TPS22810 may have thermal shutdown, but it does not have short circuit / over current protection. If you are looking for those additional features in a high side switch, then you may want to take a look at our eFuse portfolio.

    Thanks,

    Alek Kaknevicius